Skin Infections

Molluscum contagiosum

Multiple small umbilicated papules caused by MCV, common in children and immunosuppressed patients

Molluscum contagiosum clinical features

1–5 mm skin-colored umbilicated papules, often grouped linearly due to autoinoculation

Molluscum contagiosum locations

Face, neck, axillae, eyelids in children; genital area in adults

Molluscum contagiosum diagnosis

Clinical diagnosis

Molluscum contagiosum treatment

Curettage, salicylic acid, expression, cryotherapy, laser

HSV infection

Primary or recurrent infection with HSV-1 or HSV-2

HSV pathogenesis

Enters skin → replicates locally → migrates to sensory ganglia → latency → reactivation by triggers

HSV triggers

UV light, fever, menstruation, stress, immunosuppression

HSV incubation period

6–8 days

HSV clinical lesions

Group of vesicles on erythematous base that rupture into erosions

HSV-1 epidemiology

Acquired in childhood; high recurrence rate in orofacial area

HSV-2 epidemiology

Associated with sexual activity; common cause of genital herpes

Primary orofacial HSV

Herpetic gingivostomatitis with diffuse painful erosions and systemic symptoms

Recurrent orofacial HSV

Grouped vesicles on lips, chin, or periorbital area (herpes labialis)

Primary genital HSV

Painful vesicles → superficial ulcers, dysuria, lymphadenopathy, systemic symptoms

Recurrent genital HSV

Group of vesicles on erythematous base; usually milder, often HSV-2

Varicella definition

Highly contagious VZV infection causing polymorphic vesicular rash

Varicella clinical features

Macules → vesicles → pustules → crusts with all stages present simultaneously

Varicella itching

Strongly pruritic lesions

Varicella adult complications

Severe disease, VZV pneumonia

Varicella pregnancy risk

Embryopathy (1st/2nd trimester) or congenital varicella (3rd trimester)

Varicella treatment

Lotions, antibiotics for secondary infection, acyclovir in severe cases

Varicella immunization

Prevents infection and complications

Herpes zoster definition

Segmental vesicular eruption due to reactivation of latent VZV

Herpes zoster prodrome

Burning or stabbing dermatomal pain before rash

Herpes zoster rash

Unilateral grouped vesicles respecting midline

Herpes zoster complications

Ocular involvement, ear involvement, Ramsay Hunt syndrome, postherpetic neuralgia

Herpes zoster treatment

Acyclovir ideally within 48 hours + drying lotions

HPV infection

DNA virus causing warts on skin or mucosa; some types oncogenic

HPV oncogenic types

HPV 16 and 18 associated with cervical cancer

Verruca vulgaris

Common wart with hyperkeratotic papillary surface and thrombosed capillaries

Verruca vulgaris diagnosis

Clinical; loss of skin lines and black dots

Verruca vulgaris treatment

Cryotherapy, salicylic acid, laser, imiquimod; high recurrence rate

Folliculitis definition

Superficial infection of hair follicle caused by Staph aureus

Folliculitis clinical features

Follicular pustules with erythematous rim; no systemic symptoms

Folliculitis risk factors

Sweating, occlusion, corticosteroids, immunosuppression

Folliculitis treatment

Topical antibiotics; systemic if extensive

Furuncle definition

Deep infection of hair follicle and surrounding tissue

Carbuncle definition

Confluence of multiple furuncles forming a large indurated plaque

Furuncle clinical features

Painful, warm, erythematous nodule that drains purulence after several days

Furuncle dangerous location

Facial furuncles may cause cavernous sinus thrombosis

Furuncle treatment

Incision and drainage, systemic antibiotics if needed

Furunculosis management

Treat Staph aureus carrier state and underlying skin diseases

Erysipelas definition

Acute non-purulent superficial infection with lymphangitis

Erysipelas causative agents

Beta-hemolytic streptococcus most common

Erysipelas clinical features

Sharply demarcated, warm, raised erythematous plaque with fever

Erysipelas common site

Lower extremities; unilateral

Erysipelas diagnosis

Clinical; labs show high CRP and leukocytosis

Erysipelas treatment

Penicillin; amoxicillin; flucloxacillin; macrolides in allergy

Impetigo definition

Contagious superficial infection caused by staph, strep, or both

Non-bullous impetigo

Thin-walled vesicles → erosions → honey-colored crusts

Non-bullous impetigo location

Face, nose, mouth region

Non-bullous impetigo complications

Poststreptococcal glomerulonephritis

Bullous impetigo

Caused by Staph exfoliative toxin targeting desmoglein-1

Bullous impetigo clinical features

Neonatal bullae that rupture into shallow erosions

Impetigo diagnosis

Clinical ± swab for culture

Impetigo treatment

Topical mupirocin or systemic antibiotics

Lyme disease definition

Infection by Borrelia burgdorferi transmitted by Ixodes ticks

Lyme transmission time

Transmission usually requires >36 hours of tick attachment

Lyme disease stage 1

Erythema migrans: expanding annular erythema with central clearing

Lyme disease stage 2

Lymphocytoma, neurologic signs (meningoradiculitis), cardiac AV block

Lyme disease stage 3

Acrodermatitis chronica atrophicans with skin atrophy and neuropathy

Lyme disease diagnosis

Serology: IgM early, IgG late; CSF for neuroborreliosis

Lyme disease systemic symptoms

Headache, malaise, arthralgia, myalgia, fever

Dermatomycoses definition

Superficial fungal infections of skin, hair, and nails

Dermatophyte genera

Microsporum, Trichophyton, Epidermophyton

Dermatophyte transmission

Human-to-human, animal-to-human, or soil-to-human

Fungal infection risk factors

Immunosuppression, diabetes, sweating, tight clothing, humidity

Tinea corporis

Annular erythematosquamous plaque with central clearing (ringworm)

Tinea inguinalis

Fungal infection of groin with itching and erythema

Tinea pedis

Interdigital maceration or hyperkeratotic scaling (“athlete’s foot”)

Tinea pedis complication

Entry portal for erysipelas or cellulitis

Interdigital tinea

Maceration between toes, especially 3rd–4th spaces

Hyperkeratotic tinea

Moccasin-type scaling over soles

Tinea capitis

Ectothrix or endothrix infection causing alopecia and scaling

Tinea capitis ectothrix

Pseudo-alopecia with scaling; green fluorescence with Wood lamp

Tinea capitis endothrix

Black-dot alopecia from broken hairs

Kerion celsi

Severe inflammatory boggy mass due to tinea capitis

Onychomycosis

Fungal nail infection causing thickened, discolored nails

Onychomycosis risk factors

Age, trauma, circulation problems, humidity

Candidiasis

Fungal infection involving skin folds or mucosa; favored by moisture and antibiotics

Dermatomycoses diagnosis

Clinical exam, Wood lamp, KOH microscopy, culture, PCR

KOH prep finding

Hyphae or spores indicating fungal infection